The recent snow has been blown around by the strong winds. These wind slabs are sitting on a weak faceted base. Perfect recipe for avalanches.
Confidence
Moderate - Due to the number and quality of field observations
Weather Forecast
The winds are supposed to stay strong (75km/hr) in the alpine from the SW until Friday. The next pulse of snow is forecast to start in the wee hours of Friday morning. Alpine temperatures on Thursday will be around -7c.
Avalanche Summary
No recent avalanches were observed on Wednesday Dec 12 but the visibility was poor to see much.
Snowpack Summary
The alpine has received 10-15cm of new snow which has been blown into wind slabs from the strong SW winds. Expect the westerly slopes to be scoured of snow and the lee sides and cross loaded gullies to be well loaded with snow. More snow and 75km/hr winds for Thursday will continue to grow the wind slabs. Expect these new slabs to be touchy and if they do release, they will probably step down into the weak base layers and involve the whole snowpack.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.